219 measurementsis estimated to be 4% orless for 10.85 < E < 11.0 eV and £& > 11.4 eV, and 2% orless for other photoionization cross sections, ¢:(¢; = na), are also given in the tables. ater E values. The photoionization yield, , is the probability that photon absorption produces ionization. Tor some gases the measured 7 values were pressure dependent in the energy region just below the ionization potential,?: » and in these cases footnotes indicate the pressures used. They values fora given EZ have a relative uncertainty of approximately (2% of the 7 value) + 0.002, but the absolute (Z) values are more uncertain because of the uncertainties in the 7(Z) values for acetone,” which was used as a secondary standard. The “pelt PPEPged 2 ENOa bibs wee TABLE 80. AssorPTion Cross SECTIONS, PHOTOIONIZATION YIELDS, AND PHOTOIONIZATION Cross SECTIONS FOR ACETYLENE AND ACETYLENE-d, lengthA eV 1052.4 1055.6 1058.6 1061.7 1065.2 1069.9 1072.8 1076.8 1079.7 1081.6 1084.5 1088.7 1090.0 1092.4 1094.7 11.78 11.75 11.71 11.68 11.64 11.59 11.56 11.51 1148 11.46 11.43 11.39 11.37 11.35 11.33, 27.56 27.13 27.70 28.17 29.08 25.47 27.10 28.32 27.86 28.30 22.58 35.20 20.76 31.02 20.60 1.31 0.67 0.62 0.56 0.50 0.54 0.36 0.43 0.38 0.51 0.40 0.26 0.31 0.49 0.29 11.28 11.25 13.52 44.42 0.58 0.48 1098.1 11.29 1099.5 1102.0 - (a) 1 Mb jen, Mb®) cx, Mb| —_ 22.71 1O- 18 em?. (bh) Pressure ~(0.2 torr, 0.40 a op, Mb op, Mb mp 10} 10 9 10 10 10 10 10 10 10 12 10) 12 10 12 27.15 27.21 27.98 (27.60 29.09 27.74 26.20 28.05 25.78 26.78 28.51 27.81 35.45 18.13 20.67 0.68 0.52 0.46 0.35 0.54 0.43 0.37 0.21 0.42 0.26 0.34 0.27 0.50 0.36 0.26 10 10 10 10 10 10 10 10 10 10 10 10 10 12 12 14 10 17.66 11.83 0.92 0.40 13 12 12 54.80 1.19 7 ms ou ,Mb o>, Mb 0.864 0.808 0.359 0.906 0.870 0.880 0.873 0.873 0.836 0.868 0.710 0.706 0.676 0.721 0.641 0.668 0.652 0.660 0.621 0.702 0.667 0.650 0.154| O.121| 0.040% ; 0.0200] 0.012 0.038 0.018 0.011 23. 80 23. 29 24.10 24.59 24.32 18.07 18.33 18.16 18.17 17.56 15.06 5.41| o.g2)] 0.39 0.38 24.24 24.66 24.61 24.10 25. 25 19.59 18.90 18.75 17.03 18.81 18.52 3 agen a4 0.69 0.23 0.001 0.000 0.02 0.02 0.08 0.05 0.002 ™ 0.002 0.005 0.004 0.05 0.09